Hybrid vehicle

ABSTRACT

A hybrid vehicle includes: an internal combustion engine; a rotating electric machine; a planetary gear mechanism to which the internal combustion engine, the rotating electric machine and an output shaft are connected; a catalyst that purifies exhaust gas of the internal combustion engine; and a controller that controls the internal combustion engine and the rotating electric machine. The controller controls the internal combustion engine and the rotating electric machine to perform catalyst temperature control to shift an operating point on a map representing a relationship between rotation speed of the internal combustion engine and torque generated by the internal combustion engine so that the catalyst has a temperature within an appropriate temperature range. Degradation of the catalyst can be suppressed without deteriorating the function of the catalyst.

This nonprovisional application is based on Japanese Patent ApplicationNo. 2019-066084 filed with the Japan Patent Office on Mar. 29, 2019, theentire contents of which are hereby incorporated by reference.

BACKGROUND Field

The present disclosure relates to a hybrid vehicle, and morespecifically to a hybrid vehicle including an internal combustion enginewith a forced induction device.

Description of the Background Art

Japanese Patent Laying-Open No. 2015-058924 discloses a hybrid vehiclehaving mounted therein an internal combustion engine equipped with aturbo forced induction device, and a motor generator.

SUMMARY

Such a hybrid vehicle uses energy of exhaust gas for boosting suctionedair by a turbocharger, and accordingly, the exhaust gas's temperaturetends to be lowered. As a result, exhaust gas flowing into a catalystwhich purifies exhaust gas of the engine has a reduced temperature, and,as a component of sulfur contained in fuel, lubricant or the likeadsorbs to the catalyst, the catalyst may be poisoned by sulfur. As aresult, the catalyst would poorly function. In such a case, increasingthe temperature of the exhaust gas can recover the catalyst from sulfurpoisoning. Further, when the catalyst has excessively high temperature,degradation of the catalyst may be facilitated.

The present disclosure has been made to solve the above problem, and anobject thereof is to provide a hybrid vehicle that can suppressdegradation of a catalyst without deteriorating the function of thecatalyst.

According to the present disclosure, a hybrid vehicle includes: aninternal combustion engine; a rotating electric machine; a planetarygear mechanism to which the internal combustion engine, the rotatingelectric machine and an output shaft are connected; a catalyst thatpurifies exhaust gas of the internal combustion engine; and a controllerthat controls the internal combustion engine and the rotating electricmachine. The controller controls the internal combustion engine and therotating electric machine to perform catalyst temperature control toshift an operating point on a map representing a relationship betweenrotation speed of the internal combustion engine and torque generated bythe internal combustion engine so that the catalyst has a temperaturewithin an appropriate temperature range.

According to such a configuration the catalyst can have temperaturewithin the appropriate temperature range. As a result, a hybrid vehiclethat can suppress degradation of the catalyst without deteriorating thefunction of the catalyst.

Preferably, the controller shifts the operating point on an isopowerline. According to such a configuration, the internal combustion enginecan have a fixed output even when the operating point is shifted. As aresult, the vehicle can continue to travel without significantlyincreasing or decreasing an amount of power charged/discharged to/from abattery while keeping a driving force constantly.

When the catalyst has a temperature lower than the appropriatetemperature range the catalyst is poisoned by a prescribed substance andthus has its purifying ability impaired, whereas when the catalyst has atemperature within the appropriate temperature range or higher thecatalyst is recovered from poisoning and thus has its purifying abilityrestored. Preferably, the controller controls the internal combustionengine and the rotating electric machine to perform the catalysttemperature control when a condition for recovering the catalyst frompoisoning is satisfied.

According to such a configuration, when recovering the catalyst frompoisoning, a control can be applied to allow the catalyst to have atemperature within the appropriate temperature range. As a result, thecatalyst can be recovered from poisoning and the catalyst's purifyingability can be restored.

Still preferably, the internal combustion engine includes a forcedinduction device which uses energy of exhaust gas emitted from theinternal combustion engine to boost suctioned air to be fed to theinternal combustion engine. A boost line is determined on the map, andthe forced induction device boosts suctioned air when the torquegenerated by the internal combustion engine indicated by an operatingpoint on the map exceeds the boost line. When the torque generated bythe internal combustion engine indicated by the operating point on themap exceeds the boost line, the controller shifts the operating pointbelow the boost line to allow the catalyst to have a temperature withinthe appropriate temperature range or higher for a longer period of timethan when the operating point is not shifted.

According to such a configuration the catalyst can have a temperaturewithin the appropriate temperature range or higher for an increasedperiod of time. As a result, the catalyst can be recovered frompoisoning and the catalyst's purifying ability can be restored.

The catalyst degrades when it has a temperature higher than theappropriate temperature range. Preferably the controller controls theinternal combustion engine and the rotating electric machine to performthe catalyst temperature control when the catalyst has a temperatureexceeding the appropriate temperature range. According to such aconfiguration, when the catalyst has a temperature exceeding theappropriate temperature range, control can be applied to allow thecatalyst to have a temperature within the appropriate temperature range.As a result, degradation of the catalyst can be suppressed.

Still preferably, the internal combustion engine includes a forcedinduction device which uses energy of exhaust gas emitted from theinternal combustion engine to boost suctioned air to be fed to theinternal combustion engine. A boost line is determined on the map, andthe forced induction device boosts suctioned air when the torquegenerated by the internal combustion engine indicated by an operatingpoint on the map exceeds the boost line. When the torque generated bythe internal combustion engine indicated by the operating point on themap is below the boost line, the controller shifts the operating pointto exceed the boost line to allow the catalyst to have a temperaturewithin the appropriate temperature range or lower for a longer period oftime than when the operating point is not shifted.

According to such a configuration the catalyst can have a temperaturewithin the appropriate temperature range or lower for an increasedperiod of time. As a result, degradation of the catalyst can besuppressed.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an exemplary configuration of a drive systemof a hybrid vehicle according to an embodiment of the presentdisclosure.

FIG. 2 is a diagram showing an exemplary configuration of an engineincluding a turbocharger.

FIG. 3 is a block diagram showing an exemplary configuration of acontroller.

FIG. 4 is a diagram for illustrating an operating point of the engine.

FIG. 5 is a nomographic chart representing a relationship betweenrotation speed and torque that the engine, a first MG, and an outputelement have.

FIG. 6 is a nomographic chart representing a relationship betweenrotation speed and torque that the engine, the first MG, and the outputelement have.

FIG. 7 is a nomographic chart representing a relationship betweenrotation speed and torque that the engine, the first MG, and the outputelement have.

FIG. 8 shows an optimum fuel efficiency line which is an exemplaryrecommended operation line for the engine.

FIG. 9 is a flowchart of an example of a basic computation process fordetermining operating points for the engine, the first MG, and thesecond MG.

FIG. 10 is a flowchart of a catalyst temperature related process of thepresent embodiment.

FIG. 11 is a diagram for illustrating how an operating point is shiftedby catalyst temperature control.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present disclosure will be described in detailbelow with reference to the drawings. The same or corresponding elementsin the drawings have the same reference characters allotted anddescription thereof will not be repeated.

<Drive System of Hybrid Vehicle>

FIG. 1 is a diagram showing an exemplary configuration of a drive systemof a hybrid vehicle (which is simply denoted as a vehicle below) 10according to an embodiment of the present disclosure. As shown in FIG. 1, vehicle 10 includes as a drive system, a controller 11 as well as anengine 13, a first motor generator (which is denoted as a first MGbelow) 14, and a second motor generator (which is denoted as a second MGbelow) 15 that serve as motive power sources for travelling. Engine 13includes a turbo charger 47.

First MG 14 and second MG 15 each perform a function as a motor thatoutputs torque by being supplied with driving electric power and afunction as a generator that generates electric power by being suppliedwith torque. An alternating current (AC) rotating electric machine isemployed for first MG 14 and second MG 15. The AC rotating electricmachine is, for example, a permanent magnet type or similar synchronousmotor including a rotor having a permanent magnet embedded, or aninduction motor.

First MG 14 and second MG 15 are electrically connected to a battery 18with a power control unit (PCU) 81 being interposed. PCU 81 includes afirst inverter 16 that supplies and receives electric power to and fromfirst MG 14, a second inverter 17 that supplies and receives electricpower to and from second MG 15, battery 18, and a converter 83 thatsupplies and receives electric power to and from first inverter 16 andsecond inverter 17.

For example, converter 83 can up-convert electric power from battery 18and supply up-converted electric power to first inverter 16 or secondinverter 17. Alternatively, converter 83 can down-convert electric powersupplied from first inverter 16 or second inverter 17 and supplydown-converted electric power to battery 18.

First inverter 16 can convert direct current (DC) power from converter83 into AC power and supply AC power to first MG 14. Alternatively,first inverter 16 can convert AC power from first MG 14 into DC powerand supply DC power to converter 83.

Second inverter 17 can convert DC power from converter 83 into AC powerand supply AC power to second MG 15. Alternatively, second inverter 17can convert AC power from second MG 15 into DC power and supply DC powerto converter 83.

Battery 18 is a rechargeably configured electric power storagecomponent. Battery 18 for example includes a rechargeable battery suchas a lithium ion battery, a nickel metal hydride battery or the like, ora power storage element such as an electric double layer capacitor, orthe like. The lithium ion secondary battery is a secondary battery inwhich lithium is adopted as a charge carrier, and may include not only ageneral lithium ion secondary battery containing a liquid electrolytebut also what is called an all-solid-state battery containing a solidelectrolyte.

Battery 18 can store power generated by first MG 14 and received viafirst inverter 16 and can supply the stored power to second MG 15 viasecond inverter 17. Further, battery 18 can also store power generatedby second MG 15 when the vehicle is decelerated, and received via secondinverter 17, and can also supply the stored power to first MG 14 viafirst inverter 16 when engine 13 is started.

PCU 81 charges battery 18 with electric power generated by first MG 14or second MG 15 or drives first MG 14 or second MG 15 with electricpower from battery 18.

Engine 13 and first MG 14 are coupled to a planetary gear mechanism 20.Planetary gear mechanism 20 transmits drive torque output from engine 13by splitting drive torque into drive torque to first MG 14 and drivetorque to an output gear 21. Planetary gear mechanism 20 includes asingle-pinion planetary gear mechanism and is arranged on an axis Cntcoaxial with an output shaft 22 of engine 13.

Planetary gear mechanism 20 includes a sun gear S, a ring gear Rarranged coaxially with sun gear S, a pinion gear P meshed with sun gearS and ring gear R, and a carrier C holding pinion gear P in a rotatableand revolvable manner. Engine 13 has output shaft 22 coupled to carrierC. A rotor shaft 23 of first MG 14 is coupled to sun gear S. Ring gear Ris coupled to output gear 21.

Carrier C to which torque output from engine 13 is transmitted serves asan input element, ring gear R that outputs torque to output gear 21serves as an output element, and sun gear S to which rotor shaft 23 iscoupled serves as a reaction force element. That is, planetary gearmechanism 20 divides an output of engine 13 for the side of first MG 14and the side of output gear 21. First MG 14 is controlled to outputtorque in accordance with torque output from engine 13.

A countershaft 25 is arranged in parallel to axis Cnt. Countershaft 25is attached to a driven gear 26 meshed with output gear 21. A drive gear27 is attached to countershaft 25, and drive gear 27 is meshed with aring gear 29 in a differential gear 28 representing a final reductiongear. A drive gear 31 attached to a rotor shaft 30 in second MG 15 ismeshed with driven gear 26. Therefore, torque output from second MG 15is added at driven gear 26 to torque output from output gear 21. Torquethus combined is transmitted to drive wheel 24 with driveshafts 32 and33 extending laterally from differential gear 28 being interposed. Astorque is transmitted to drive wheel 24, driving force is generated invehicle 10.

<Configuration of Engine>

FIG. 2 is a diagram showing an exemplary configuration of engine 13including turbo charger 47. Engine 13 is, for example, an in-linefour-cylinder spark ignition internal combustion engine. As shown inFIG. 2 , engine 13 includes, for example, an engine main body 40 formedwith four cylinders 40 a, 40 b, 40 c, and 40 d being aligned in onedirection.

One ends of intake ports and one ends of exhaust ports formed in enginemain body 40 are connected to cylinders 40 a, 40 b, 40 c, and 40 d. Oneend of the intake port is opened and closed by two intake valves 43provided in each of cylinders 40 a, 40 b, 40 c, and 40 d, and one end ofthe exhaust port is opened and closed by two exhaust valves 44 providedin each of cylinders 40 a, 40 b, 40 c and 40 d. The other ends of theintake ports of cylinders 40 a, 40 b, 40 c, and 40 d are connected to anintake manifold 46. The other ends of the exhaust ports of cylinders 40a, 40 b, 40 c, and 40 d are connected to an exhaust manifold 52.

In the present embodiment, engine 13 is, for example, a direct injectionengine and fuel is injected into each of cylinders 40 a, 40 b, 40 c, and40 d by a fuel injector (not shown) provided at the top of eachcylinder. An air fuel mixture of fuel and intake air in cylinders 40 a,40 b, 40 c, and 40 d is ignited by an ignition plug 45 provided in eachof cylinders 40 a, 40 b, 40 c, and 40 d.

FIG. 2 shows intake valve 43, exhaust valve 44, and ignition plug 45provided in cylinder 40 a and does not show intake valve 43, exhaustvalve 44, and ignition plug 45 provided in other cylinders 40 b, 40 c,and 40 d.

Engine 13 is provided with turbo charger 47 that uses exhaust energy toboost suctioned air. Turbo charger 47 includes a compressor 48 and aturbine 53.

An intake air passage 41 has one end connected to intake manifold 46 andthe other end connected to an air inlet. Compressor 48 is provided at aprescribed position in intake air passage 41. An air flow meter 50 thatoutputs a signal in accordance with a flow rate of air that flowsthrough intake air passage 41 is provided between the other end (airinlet) of intake air passage 41 and compressor 48. An intercooler 51that cools intake air pressurized by compressor 48 is disposed in intakeair passage 41 provided downstream from compressor 48. An intakethrottle valve (throttle valve) 49 that can regulate a flow rate ofintake air that flows through intake air passage 41 is provided betweenintercooler 51 and intake manifold 46 of intake air passage 41.

An exhaust passage 42 has one end connected to exhaust manifold 52 andthe other end connected to a muffler (not shown). Turbine 53 is providedat a prescribed position in exhaust passage 42. In exhaust passage 42, abypass passage 54 that bypasses exhaust upstream from turbine 53 to aportion downstream from turbine 53 and a waste gate valve 55 provided inbypass passage 54 and capable of regulating a flow rate of exhaustguided to turbine 53 are provided. Therefore, a flow rate of exhaustthat flows into turbine 53, that is, a boost pressure for suctioned air,is regulated by controlling a position of waste gate valve 55. Exhaustthat passes through turbine 53 or waste gate valve 55 is purified by astart-up catalytic converter 56 and an aftertreatment apparatus 57provided at prescribed positions in exhaust passage 42, and thereafteremitted into the atmosphere. Start-up catalytic converter 56 andaftertreatment apparatus 57 include a three-way catalyst for example.

A three-way catalyst is a catalyst which purifies nitrogen oxides (NOx),carbon monoxide (CO), and uncombusted hydrocarbon (HC) contained inexhaust gas passing through an exhaust gas passage of engine 13. Thethree-way catalyst reduces NOx to nitrogen and oxygen in the presence ofa reducing gas (H₂, CO, or hydrocarbon), oxidizes carbon monoxide tocarbon dioxide in the presence of an oxidizing gas, and oxidizesuncombusted hydrocarbon (HC) to carbon dioxide and water in the presenceof an oxidizing gas. In order for the three-way catalyst to efficientlyprovide oxidization or reduction, it is necessary for engine 13 tocombust fuel completely at a theoretical air/fuel ratio with no oxygenremaining (i.e., stoichiometrically). A lean state with oxygen remainingis not preferable for purifying NOx by the three-way catalyst. If thecatalyst has a temperature lower than an appropriate temperature range(an activation temperature range), the three-way catalyst inefficientlyworks.

Start-up catalytic converter 56 is provided at an upstream portion (aportion closer to the combustion chamber) of exhaust passage 42, andaccordingly, it is heated to activation temperature within a shortperiod of time after engine 13 is started. Furthermore, aftertreatmentapparatus 57 located downstream purifies HC, CO and NOx that could notbe purified by startup catalytic converter 56.

Engine 13 is provided with an exhaust gas recirculation (EGR) apparatus58 that has exhaust flow into intake air passage 41. EGR apparatus 58includes an EGR passage 59, an EGR valve 60, and an EGR cooler 61. EGRpassage 59 allows some of exhaust to be taken out of exhaust passage 42as EGR gas and guides EGR gas to intake air passage 41. EGR valve 60regulates a flow rate of EGR gas that flows through EGR passage 59. EGRcooler 61 cools EGR gas that flows through EGR passage 59. EGR passage59 connects a portion of exhaust passage 42 between start-up catalyticconverter 56 and aftertreatment apparatus 57 to a portion of intake airpassage 41 between compressor 48 and air flow meter 50.

<Configuration of Controller>

FIG. 3 is a block diagram showing an exemplary configuration ofcontroller 11. As shown in FIG. 3 , controller 11 includes a hybridvehicle (HV)-electronic control unit (ECU) 62, an MG-ECU 63, and anengine ECU 64.

HV-ECU 62 is a controller that controls engine 13, first MG 14, andsecond MG 15 in coordination. MG-ECU 63 is a controller that controls anoperation by PCU 81. Engine ECU 64 is a controller that controls anoperation by engine 13.

HV-ECU 62, MG-ECU 63, and engine ECU 64 each include an input and outputapparatus that supplies and receives signals to and from various sensorsand other ECUs that are connected, a storage that serves for storage ofvarious control programs or maps (including a read only memory (ROM) anda random access memory (RAM)), a central processing unit (CPU) thatexecutes a control program, and a counter that counts time.

A vehicle speed sensor 66, an accelerator position sensor 67, a first MGrotation speed sensor 68, a second MG rotation speed sensor 69, anengine rotation speed sensor 70, a turbine rotation speed sensor 71, aboost pressure sensor 72, a battery monitoring unit 73, a first MGtemperature sensor 74, a second MG temperature sensor 75, a first INVtemperature sensor 76, a second INV temperature sensor 77, a catalysttemperature sensor 78, and a turbine temperature sensor 79 are connectedto HV-ECU 62.

Vehicle speed sensor 66 detects a speed of vehicle 10 (vehicle speed).Accelerator position sensor 67 detects an amount of pressing of anaccelerator pedal (accelerator position). First MG rotation speed sensor68 detects a rotation speed of first MG 14. Second MG rotation speedsensor 69 detects a rotation speed of second MG 15. Engine rotationspeed sensor 70 detects a rotation speed of output shaft 22 of engine 13(engine rotation speed). Turbine rotation speed sensor 71 detects arotation speed of turbine 53 of turbo charger 47. Boost pressure sensor72 detects a boost pressure of engine 13. First MG temperature sensor 74detects an internal temperature of first MG 14 such as a temperatureassociated with a coil or a magnet. Second MG temperature sensor 75detects an internal temperature of second MG 15 such as a temperatureassociated with a coil or a magnet. First INV temperature sensor 76detects a temperature of first inverter 16 such as a temperatureassociated with a switching element. Second INV temperature sensor 77detects a temperature of second inverter 17 such as a temperatureassociated with a switching element. Catalyst temperature sensor 78detects a temperature of aftertreatment apparatus 57. Turbinetemperature sensor 79 detects a temperature of turbine 53. Varioussensors output signals indicating results of detection to HV-ECU 62.

Battery monitoring unit 73 obtains a state of charge (SOC) representinga ratio of a remaining amount of charge to a full charge capacity ofbattery 18 and outputs a signal indicating the obtained SOC to HV-ECU62. Battery monitoring unit 73 includes, for example, a sensor thatdetects a current, a voltage, and a temperature of battery 18. Batterymonitoring unit 73 obtains an SOC by calculating the SOC based on thedetected current, voltage, and temperature of battery 18. Various knownapproaches such as an approach by accumulation of current values(coulomb counting) or an approach by estimation of an open circuitvoltage (OCV) can be adopted as a method of calculating an SOC.

<Control of Travelling of Vehicle>

Vehicle 10 configured as above can be set or switched to such atravelling mode as a hybrid (HV) travelling mode in which engine 13 andsecond MG 15 serve as motive power sources and an electric (EV)travelling mode in which the vehicle travels with engine 13 remainingstopped and second MG 15 being driven by electric power stored inbattery 18. Setting of and switching to each mode is made by HV-ECU 62.HV-ECU 62 controls engine 13, first MG 14, and second MG 15 based on theset or switched travelling mode.

The EV travelling mode is selected, for example, in a low-load operationregion where a vehicle speed is low and requested driving force is low,and refers to a travelling mode in which an operation by engine 13 isstopped and second MG 15 outputs driving force.

The HV travelling mode is selected in a high-load operation region wherea vehicle speed is high and requested driving force is high, and refersto a travelling mode in which combined torque of drive torque of engine13 and drive torque of second MG 15 is output.

In the HV travelling mode, in transmitting drive torque output fromengine 13 to drive wheel 24, first MG 14 applies reaction force toplanetary gear mechanism 20. Therefore, sun gear S functions as areaction force element. In other words, in order to apply engine torqueto drive wheel 24, first MG 14 is controlled to output reaction torqueagainst engine torque. In this case, regenerative control in which firstMG 14 functions as a generator can be carried out.

Control of engine 13, first MG 14, and second MG 15 in coordinationwhile vehicle 10 operates will be described below.

HV-ECU 62 calculates requested driving force based on an acceleratorposition determined by an amount of pressing of the accelerator pedal.HV-ECU 62 calculates requested travelling power of vehicle 10 based onthe calculated requested driving force and a vehicle speed. HV-ECU 62calculates a value resulting from addition of requested charging anddischarging power of battery 18 to requested travelling power asrequested system power.

HV-ECU 62 determines whether or not activation of engine 13 has beenrequested in accordance with calculated requested system power. HV-ECU62 determines that activation of engine 13 has been requested, forexample, when requested system power exceeds a threshold value. Whenactivation of engine 13 has been requested, HV-ECU 62 sets the HVtravelling mode as the travelling mode. When activation of engine 13 hasnot been requested, HV-ECU 62 sets the EV travelling mode as thetravelling mode.

When activation of engine 13 has been requested (that is, when the HVtravelling mode is set), HV-ECU 62 calculates power requested of engine13 (which is denoted as requested engine power below). For example,HV-ECU 62 calculates requested system power as requested engine power.For example, when requested system power exceeds an upper limit value ofrequested engine power, HV-ECU 62 calculates the upper limit value ofrequested engine power as requested engine power. HV-ECU 62 outputscalculated requested engine power as an engine operation state commandto engine ECU 64.

Engine ECU 64 operates in response to the engine operation state commandinput from HV-ECU 62 to variously control each component of engine 13such as intake throttle valve 49, ignition plug 45, waste gate valve 55,and EGR valve 60.

HV-ECU 62 sets based on calculated requested engine power, an operatingpoint of engine 13 in a coordinate system defined by an engine rotationspeed and engine torque. HV-ECU 62 sets, for example, an intersectionbetween an equal power line equal in output to requested engine power inthe coordinate system and a predetermined operating line as theoperating point of engine 13.

The predetermined operating line represents a trace of variation inengine torque with variation in engine rotation speed in the coordinatesystem, and it is set, for example, by adapting the trace of variationin engine torque high in fuel efficiency through experiments.

HV-ECU 62 sets the engine rotation speed corresponding to the setoperating point as a target engine rotation speed.

As the target engine rotation speed is set, HV-ECU 62 sets a torquecommand value for first MG 14 for setting a current engine rotationspeed to the target engine rotation speed. HV-ECU 62 sets the torquecommand value for first MG 14, for example, through feedback controlbased on a difference between a current engine rotation speed and thetarget engine rotation speed.

HV-ECU 62 calculates engine torque to be transmitted to drive wheel 24based on the set torque command value for first MG 14 and sets a torquecommand value for second MG 15 so as to fulfill requested driving force.HV-ECU 62 outputs set torque command values for first MG 14 and secondMG 15 as a first MG torque command and a second MG torque command toMG-ECU 63.

MG-ECU 63 calculates a current value corresponding to torque to begenerated by first MG 14 and second MG 15 and a frequency thereof basedon the first MG torque command and the second MG torque command inputfrom HV-ECU 62, and outputs a signal including the calculated currentvalue and the frequency thereof to PCU 81.

HV-ECU 62 may request increase in boost pressure, for example, when theaccelerator position exceeds a threshold value for starting turbocharger 47, when requested engine power exceeds a threshold value, orwhen engine torque corresponding to the set operating point exceeds athreshold value.

Though FIG. 3 illustrates a configuration in which HV-ECU 62, MG-ECU 63,and engine ECU 64 are separately provided by way of example, the ECUsmay be integrated as a single ECU.

FIG. 4 is a diagram for illustrating an operating point of engine 13. InFIG. 4 , the vertical axis represents torque Te of engine 13, and thehorizontal axis represents an engine speed Ne of engine 13.

Referring to FIG. 4 , a line L1 represents a maximum torque that engine13 can output. A dotted line L2 represents a line (a boost line) atwhich turbocharger 47 starts boosting. When torque Te of engine 13exceeds boost line L2, waste gate valve 55, having been fully open, isoperated in the closing direction. Adjusting the angle of opening ofwaste gate valve 55 can adjust the flow rate of exhaust air flowing intoturbine 53 of turbocharger 47 and the boost pressure for the suctionedair can be adjusted through compressor 48. When torque Te falls belowboost line L2, waste gate valve 55 can be fully opened to inactivateturbocharger 47.

In hybrid vehicle 10, engine 13 and first MG 14 can be controlled tochange the operating point of engine 13. Also, the final vehicle drivingforce is adjustable by controlling second MG 15, and accordingly, theoperating point of engine 13 can be moved while the vehicle drive forceis adjusted (e.g., maintained). A way of moving the operating point ofengine 13 will now be described.

FIGS. 5 to 7 are nomographic charts showing the relationship between therotation speed and torque of engine 13, first MG 14, and the outputelement. FIG. 5 is a nomographic chart showing the relationship betweenthe rotation speed and torque of the respective elements before theoperating point of engine 13 is changed. FIG. 6 is a nomographic chartshowing the relationship between the rotation speed and torque of therespective elements when engine speed Ne of engine 13 is increased fromthe state shown in FIG. 5 . FIG. 7 is a nomographic chart showing therelationship between the rotation speed and torque of the respectiveelements when torque Te of engine 13 is increased from the state shownin FIG. 5 .

In each of FIGS. 5 to 7 , the output element is ring gear R coupled tocountershaft 25 (FIG. 1 ). Positions on the vertical axis represent therotation speeds of the respective elements (engine 13, first MG 14, andsecond MG 15), and spacings between the vertical axes represent the gearratio of planetary gear mechanism 20. “Te” represents a torque of engine13, and “Tg” represents a torque of first MG 14. “Tep” represents adirect torque of engine 13, and “Tm1” represents a torque obtained byconverting torque Tm of second MG 15 on the output element. The sum ofTep and Tm1 corresponds to a torque output to a drive shaft(countershaft 25). The up arrow represents a positive-going torque, adown arrow represents a negative-going torque, and an arrow lengthrepresents torque magnitude.

Referring to FIGS. 5 and 6 , the dotted line in FIG. 6 represents therelationship before engine speed Ne is increased, and corresponds to theline shown in FIG. 5 . The relationship between torque Te of engine 13and torque Tg of first MG 14 is uniquely determined by the gear ratio ofplanetary gear mechanism 20. Thus, first MG 14 can be controlled suchthat the rotation speed of first MG 14 increases with torque Tg of firstMG 14 maintained, thereby increasing engine speed Ne of engine 13 withthe driving torque maintained.

Also, referring to FIGS. 5 and 7 , engine 13 can be controlled such thatthe output (power) of engine 13 is increased, thereby increasing torqueTe of engine 13. At this time, torque Tg of first MG 14 can be increasedsuch that the rotation speed of first MG 14 does not increase, therebyincreasing torque Te of engine 13 with engine speed Ne of engine 13maintained. Since engine direct torque Tep increases along with anincrease in torque Te, second MG 15 can be controlled such that torqueTm1 decreases, thereby maintaining the torque of the drive shaft.

When torque Te of engine 13 is increased, torque Tg of first MG 14increases, leading to an increase in the power generated by first MG 14.At this time, if charging of battery 18 is not restricted, battery 18can be charged with the generated power which has been increased.

Although not particularly shown, controlling engine 13 can be controlledsuch that the output (power) of engine 13 decreases, thereby reducingtorque Te of engine 13. At this time, torque Tg of first MG 14 can bereduced such that the rotation speed of first MG 14 does not decrease,thereby reducing torque Te of engine 13 with engine speed Ne of engine13 maintained. In this case, torque Tg of first MG 14 decreases, leadingto a decrease in the power generated by first MG 14. At this time, ifdischarging of battery 18 is not restricted, discharging by battery 18can be increased to compensate for an amount of the decrease in thepower generated by first MG 14.

Referring to FIG. 4 again, a line L3 represents a recommended operationline of engine 13. In other words, engine 13 is usually controlled tomove on the recommended operation line (line L3) in which the operatingpoint determined by torque Te and engine speed Ne is set in advance.

FIG. 8 shows an optimum fuel efficiency line which is an examplerecommended operation line of engine 13. Referring to FIG. 8 , a line L5is an operation line set in advance by initial assessment test orsimulation to obtain minimum fuel consumption of engine 13. Theoperating point of engine 13 is controlled to be located on line L5,leading to optimum (minimum) fuel consumption of engine 13 for therequested power. A dotted line L6 is an isopower line of engine 13 whichcorresponds to the requested power. Note that in FIG. 4 , a dotted lineL41 represents an isopower line. Fuel consumption of engine 13 isoptimized (minimized) by controlling engine 13 such that the operatingpoint of engine 13 is a point at intersection E0 of dotted line L6 withline L5. A group of closed curves 11 in the figure shows anisoefficiency line of engine 13, in which the efficiency of engine 13 ishigher as closer to the center.

<Description of Basic Computation Process of Operating Point>

FIG. 9 is a flowchart showing an example basic computation process fordetermining the operating points of engine 13, first MG 14, and secondMG 15. A series of steps shown in this flowchart is repeatedly performedfor each prescribed period in HV-ECU 62.

Referring to FIG. 9 , HV-ECU 62 acquires information on, for example, anaccelerator position, a shift range being selected, and a vehicle speed(step S10). The accelerator position is detected by accelerator positionsensor 67, and the vehicle speed is detected by vehicle speed sensor 66.The rotation speed of a drive shaft or propeller shaft may be used inplace of the vehicle speed.

HV-ECU 62 then computes a requested driving force (torque) from theinformation acquired at step S10 using a drive force map prepared inadvance per shift range, which indicates the relationship amongrequested driving force, accelerator position, and vehicle speed (stepS15). HV-ECU 62 then multiplies the computed requested driving force bythe vehicle speed and adds prescribed loss power to a result of themultiplication, thereby computing traveling power of the vehicle (stepS20).

Then, when there is a charge/discharge request (power) of battery 18,HV-ECU 62 computes a value obtained by adding the charge/dischargerequest (charge has a positive value) to the computed traveling power assystem power (step S25). For example, the charge/discharge request canhave a greater positive value as the SOC of battery 18 is lower and havea negative value when the SOC is high.

HV-ECU 62 then determines to operate/stop engine 13 in accordance withthe computed system power and traveling power (step S30). For example,when system power is greater than a first threshold or when travelingpower is greater than a second threshold, HV-ECU 62 determines tooperate engine 13.

Then, when determining to operate engine 13, HV-ECU 62 performs theprocess of step S35 and the following processes (HV traveling mode).Although not specifically shown, when determining to stop engine 13 (EVtraveling mode), HV-ECU 62 computes torque Tm of second MG 15 based onthe requested driving force.

During operation of engine 13 (during the HV traveling mode), HV-ECU 62computes power Pe of engine 13 from the system power computed at stepS25 (step S35). Power Pe is computed by, for example, making variouscorrections to or imposing limitations on system power. The computedpower Pe of engine 13 is output to engine ECU 64 as a power command ofengine 13.

HV-ECU 62 then computes an engine speed Ne (target engine rotationspeed) of engine 13 (step S40). In the present embodiment, engine speedNe is computed such that the operating point of engine 13 is located online L3 (recommended operation line) shown in, for example, FIG. 4 .Specifically, the relationship between power Pe and engine speed Ne inwhich the operating point of engine 13 is located on line L3(recommended operation line) is prepared as a map or the like inadvance, and engine speed Ne is computed from power Pe computed at stepS35 using the map. When engine speed Ne is determined, torque Te (targetengine torque) of engine 13 is also determined. Consequently, theoperating point of engine 13 is determined.

HV-ECU 62 then computes torque Tg of first MG 14 (step S45). Torque Teof engine 13 can be estimated from engine speed Ne of engine 13, and therelationship between torque Te and torque Tg is uniquely determined inaccordance with the gear ratio of planetary gear mechanism 20, and thus,torque Tg can be computed from engine speed Ne. The computed torque Tgis output to MG-ECU 63 as a torque command of first MG 14.

HV-ECU 62 further computes engine direct torque Tep (step S50). Sincethe relationship between engine direct torque Tep and torque Te (ortorque Tg) is uniquely determined in accordance with the gear ratio ofplanetary gear mechanism 20, engine direct torque Tep can be computedfrom the computed torque Te or torque Tg.

HV-ECU 62 finally computes torque Tm of second MG 15 (step S50). TorqueTm is determined such that the requested driving force (torque) computedat step S15 can be obtained, and can be computed by subtracting enginedirect torque Tep from the requested driving force converted on theoutput shaft. The computed torque Tm is output to MG-ECU 63 as thetorque command of second MG 15.

As described above, the operating point of engine 13 and the operatingpoints of first MG 14 and second MG 15 are computed.

<Control of Temperature of Exhaust Gas>

Vehicle 10 of the present disclosure uses energy of exhaust gas forboosting suctioned air by turbocharger 47, and accordingly, the exhaustgas's temperature tends to be lowered. As a result, exhaust gas flowinginto the three-way catalyst of startup catalytic converter 56 andaftertreatment apparatus 57 that purifies exhaust gas of engine 13 has areduced temperature, and, as a component of sulfur contained in fuel,lubricant or the like adsorbs to the three-way catalyst, the three-waycatalyst may be poisoned by sulfur. As a result, a function of thethree-way catalyst, such as purification, would be impaired. In such acase, increasing the temperature of the exhaust gas can recover thecatalyst from sulfur poisoning. Further, when the three-way catalyst hasexcessively high temperature, degradation of the three-way catalyst maybe facilitated.

Accordingly, HV-ECU 62 according to the present disclosure controlsengine 13 and first MG 14 to perform catalyst temperature control whichshifts an operating point on a map representing a relationship betweenrotation speed of engine 13 and torque generated by engine 13 so thatthe three-way catalyst has a temperature within an appropriatetemperature range. Thus the three-way catalyst can have a temperaturewithin the appropriate temperature range. As a result, degradation ofthe three-way catalyst can be suppressed without deteriorating thefunction of the catalyst.

Hereinafter, control in the present embodiment will be described. FIG.10 is a flowchart of a catalyst temperature related process of thepresent embodiment. The catalyst temperature related process is invokedby a CPU of HV-ECU 62 from a higher-level process periodically asprescribed for control, and thus performed.

Referring to FIG. 10 , HV-ECU 62 determines whether a catalyst recoverycontrol, which will be described hereinafter, is currently performed(step S111). When it is determined that the catalyst recovery control iscurrently not performed (NO in step S111), HV-ECU 62 obtains temperatureof startup catalytic converter 56 and that of aftertreatment apparatus57 (step S112). The temperature of aftertreatment apparatus 57 isdetermined by a detection result indicated by a signal issued fromcatalyst temperature sensor 78. The temperature of startup catalyticconverter 56 is calculated, based on the detection result indicated bythe signal issued from catalyst temperature sensor 78, for example byadding a prescribed temperature to the temperature of aftertreatmentapparatus 57 specified by the detection result.

Then, it is determined whether the temperature of the catalyst ofstartup catalytic converter 56 or aftertreatment apparatus 57 is equalto or higher than a temperature at which degradation of the three-waycatalyst is facilitated (step S113). FIG. 11 is a diagram forillustrating how an operating point is shifted by catalyst temperaturecontrol. When it is determined that the catalyst has a temperature equalto or greater than a degradation facilitating temperature (YES in stepS113), then, as shown in FIG. 11 , HV-ECU 62 shifts an operating pointon an operation line to an operating point which is on an isopower lineand at which the catalyst has a temperature lower by a prescribedtemperature, that is, HV-ECU 62 starts catalyst temperature decreasingcontrol (step S114). Thereafter, HV-ECU 62 returns to a higher-levelprocess from which the catalyst temperature related process is invoked.Referring to FIG. 11 , for example, when control is applied so that anoperating point moves on the operation line L5, the catalyst temperaturedecreasing control is started to shift an operating point E2 indicatedon the operation line L5 by a star to an operating point E1 indicated onthe isopower line L6 by a black dot, at which the catalyst has atemperature lower by a prescribed temperature. Note that, although notshown, an isopower line corresponding to an output of engine 13different from the isopower line L6 exists in parallel with the isopowerline L6.

Temperature of the catalyst on the right side of a catalystisotemperature line L7 is higher than the temperature of the catalyst onthe catalyst isotemperature line L7, and temperature of the catalyst onthe left side of the catalyst isotemperature line L7 is lower than thetemperature of the catalyst on the catalyst isotemperature line L7. Notethat, although not shown, a catalyst isotemperature line correspondingto a temperature of the catalyst different than the catalystisotemperature line L7 exists in parallel with the catalystisotemperature line L7.

In a boosting area, in which generated torque Te is higher than theboost line L2, as compared with an NA area, in which generated torque Teis lower than the boost line, for the same output of engine 13, exhaustgas is deprived of energy for boosting, and accordingly, the catalysthas a reduced temperature.

When control to increase rotation speed Ne and torque Te to be generatedindicated by an operating point on the operation line L5 is currentlyapplied, the operating point of interest will be shifted to move on theoperation line L3 by being gradually changed to the operating point E1corresponding to the operating point E2 moved.

When engine 13 is currently operated while the operating point E2 on theoperation line L5 is held, the operating point of interest will beshifted to the operating point E1 on the operation line L3 correspondingto the operating point E2 and engine 13 will thus be operated.

Returning to FIG. 10 , when it is determined that the catalyst has atemperature lower than the degradation facilitating temperature (NO instep S113), HV-ECU 62 determines whether the catalyst temperaturedecreasing control started at step S114 is currently performed (stepS115). When it is determined that the catalyst temperature decreasingcontrol is currently performed (YES in step S115), HV-ECU 62 ends thecatalyst temperature decreasing control and returns the operating pointto the recommended operation line L3 (step S116) as the catalyst'stemperature is lower than the degradation facilitating temperature andit is no longer necessary to perform the catalyst temperature decreasingcontrol.

When it is determined that the catalyst temperature decreasing controlis currently not performed (NO in step S115), and after step S116,HV-ECU 62 obtains a distance travelled since immediately previously thecatalyst was recovered from poisoning (step S121). The distancetravelled since the catalyst's immediately previous recovery isaccumulated by HV-ECU 62.

HV-ECU 62 determines whether a catalyst recovery starting condition issatisfied (step S122). The catalyst recovery starting condition is forexample that the distance travelled since the catalyst's immediatelyprevious recovery has reached a prescribed distance. However, thecatalyst recovery starting condition is not limited thereto, and acondition for determining that the catalyst has been poisoned to aconsiderable extent suffices. For example, it may be a period of timefor which engine 13 is operated since the catalyst's immediatelyprevious recovery. It may be a period of time for which engine 13 isoperated or a distance travelled at a temperature lower than anappropriate temperature at which the catalyst efficiently functions(i.e., a temperature at which the catalyst is easily poisoned). An NOxsensor may be provided downstream of the catalyst, and the condition maybe that an amount of NOx that is not purified by the catalyst due tosulfur poisoning has reached a prescribed value or larger for which itcan be determined that the catalyst's purifying ability has decreased.Furthermore, recovering the catalyst may be started at any point in timewhenever vehicle 10 travels, regardless of whether the catalyst has beenpoisoned to a considerable extent. In that case, a catalyst recoverycontrol ending condition, which will be described hereinafter, caninclude a period of time elapsing since the catalyst recovery control isstarted, that is significantly smaller than that in a catalyst recoverycontrol ending condition applied in handling the catalyst poisoned to aconsiderable extent.

When it is determined that the catalyst recovery starting condition isnot satisfied (NO in step S122), HV-ECU 62 returns to a higher levelprocess from which the catalyst temperature related process is invoked.When it is determined that the catalyst recovery starting condition issatisfied (YES in step S122), an operating point on the recommendedoperation line L3 is shifted to an operating point which is on isopowerline L6 and at which the catalyst has a temperature higher by aprescribed temperature, i.e., the catalyst recovery control starts (stepS123). Thereafter, HV-ECU 62 returns to the higher level process fromwhich the catalyst temperature related process is invoked.

Referring to FIG. 11 again, for example, when control is performed sothat an operating point moves on the operation line L3, the catalystrecovery control is started to shift the operating point E1 indicated onthe operation line L3 by the black dot to the operating point E2indicated on the isopower line L6 by the star, at which the catalyst hasa temperature higher by a prescribed temperature.

When control to increase rotation speed Ne and torque Te to be generatedindicated by an operating point on the operation line L3 is currentlyapplied, the operating point of interest will be shifted to move on theoperation line L5 by being gradually changed to the operating point E2corresponding to the operating point E1 moved.

When engine 13 is currently operated while the operating point E1 on theoperation line L3 is held, the operating point of interest will beshifted to the operating point E2 on the operation line L5 correspondingto the operating point E1 and engine 13 will thus be operated.

Returning to FIG. 10 , when it is determined that the catalyst recoverycontrol is currently performed (YES in step S111), HV-ECU 62 determineswhether the catalyst recovery control ending condition is satisfied(step S124). The catalyst recovery control ending condition is, forexample, that a prescribed period of time has elapsed since the catalystrecovery control was started. However, the catalyst recovery controlending condition is not limited thereto, and a condition for determiningthat the catalyst has been recovered from poisoning to a considerableextent suffices. For example, it may be that a cumulative period of timefor which the catalyst has a temperature suitable for recovery since thecatalyst recovery control was started has reached a prescribed period oftime, or may be that a distance travelled since the catalyst recoverycontrol was started has reached a prescribed distance. When it isdetermined that the catalyst recovery control ending condition issatisfied (YES in step S124), HV-ECU 62 ends the catalyst recoverycontrol and returns the operating point to the recommended operationline L3 (step S125).

When it is determined that the catalyst recovery control endingcondition is not satisfied (NO in step S124), and after step S125,HV-ECU 62 returns to the higher level process from which the catalysttemperature related process is invoked.

<Modification>

(1) In the above-described embodiment, the catalyst is a three-waycatalyst. This is not exclusive, however, and the catalyst may be acatalyst of a type different from the three-way catalyst, e.g., a GPF(gasoline particulate filter) plus the function of the three-waycatalyst.

(2) In the above-described embodiment, as shown in FIG. 2 , the forcedinduction device is a so-called turbocharger, 47, which is driven byenergy of exhaust gas. This is not exclusive, however, and the forcedinduction device may alternatively be a mechanical forced inductiondevice driven by rotation of an engine or by a motor. Furthermore, theforced induction device may be dispensed with.

(3) In the above-described embodiment, as shown in FIG. 11 , rotationspeed is not particularly limited in an area in which generated torqueTe is low. This is not exclusive, however, and when the catalystrecovery control is performed, rotation speed of engine 13 indicated byan operating point may be controlled to be less than a prescribed value.The prescribed value is an average rotation speed value for which aperson in vehicle 10 feels uncomfortable with noise and vibration whenrotation speed is equal to or faster than the prescribed value. Thusnoise and vibration generated from engine 13 can be suppressed even whencontrol is applied so that the catalyst has a temperature within anappropriate temperature range.

(4) In the above-described embodiment, an operating point is shifted onan isopower line, as indicated in FIG. 10 at steps S114 and S123. Thisis not exclusive, however, and the operating point may be shifted to anoperating point more or less offset from the isopower line insofar asexhaust gas has a different temperature at that operating point.

(5) The above-described embodiment can be regarded as disclosure of ahybrid vehicle such as vehicle 10. Further, the above-describedembodiment can be regarded as disclosure of a controller, such as HV-ECU62, for a hybrid vehicle. Further, the above-described embodiment can beregarded as a disclosure of a control method in which a controllerperforms the catalyst temperature related process shown in FIG. 10 .Further, the above-described embodiment can be regarded as disclosure ofa program of the FIG. 10 catalyst temperature related process performedby the controller.

<Effect>

(1) As shown in FIGS. 1 to 3 , vehicle 10 includes engine 13, first MG14, planetary gear mechanism 20 to which engine 13, first MG 14, andcounter shaft 25 are connected, a catalyst that purifies exhaust gas ofengine 13 (e.g., startup catalytic converter 56, aftertreatmentapparatus 57, etc.), and HV-ECU 62 configured to control engine 13 andfirst MG 14. As shown in FIGS. 10 and 11 , HV-ECU 62 controls engine 13and first MG 14 to perform catalyst temperature control to shift anoperating point on the FIG. 4 map representing a relationship betweenrotation speed of engine 13 and torque generated by engine 13 so thatthe catalyst has a temperature within an appropriate temperature range.

Thus the catalyst can have a temperature within the appropriatetemperature range. As a result, degradation of the catalyst can besuppressed without deteriorating the function of the catalyst.

(2) As shown in FIGS. 10 and 11 , HV-ECU 62 shifts an operating point onan isopower line. Thus engine 13 can provide a fixed output even whenthe operating point is shifted. As a result, the vehicle can continue totravel without significantly increasing or decreasing an amount of powercharged/discharged to/from battery 18 while keeping a driving forceconstantly.

(3) When the catalyst has a temperature lower than the appropriatetemperature range the catalyst is poisoned by a prescribed substance(e.g., sulfur) and thus has its purifying ability impaired, whereas whenthe catalyst has a temperature within the appropriate temperature rangeor higher the catalyst is recovered from poisoning and thus has itspurifying ability restored. As shown in FIG. 10 , HV-ECU 62 controlsengine 13 and first MG 14 to perform catalyst temperature control when acondition for recovering the catalyst from poisoning is satisfied.

Thus, when recovering the catalyst from poisoning, a control can beapplied to allow the catalyst to have a temperature within theappropriate temperature range. As a result, the catalyst can berecovered from poisoning and the catalyst's purifying ability can berestored.

(4) As shown in FIG. 2 , engine 13 includes turbocharger 47 which usesenergy of exhaust gas emitted from engine 13 to boost suctioned air tobe fed to engine 13. As shown in FIG. 4 , the boost line L2 determinedon the map is such that turbocharger 47 boosts suctioned air when thetorque generated by engine 13 indicated by an operating point on the mapexceeds the boost line L2. As shown in FIGS. 10 and 11 , when the torquegenerated by engine 13 indicated by the operating point on the mapexceeds the boost line L2, HV-ECU 62 shifts the operating point belowthe boost line to allow the catalyst to have a temperature within theappropriate temperature range or higher for a longer period of time thanwhen the operating point is not shifted.

Thus the catalyst can have a temperature within the appropriatetemperature range or higher for an increased period of time. As aresult, the catalyst can be recovered from poisoning and the catalyst'spurifying ability can be restored. Note that the operating point belowthe boost line L2 enters the NA area, and when this is compared with theboosting area, the former allows engine 13 to operate in a leanatmosphere with a lower air-fuel ratio and can thus facilitaterecovering the catalyst from poisoning.

(5) The catalyst degrades when it has a temperature higher than theappropriate temperature range. As shown in FIG. 10 , HV-ECU 62 controlsengine 13 and first MG 14 to perform catalyst temperature decreasingcontrol when the catalyst has a temperature exceeding the appropriatetemperature range. Thus, when the catalyst has a temperature exceedingthe appropriate temperature range, control can be applied to allow thecatalyst to have a temperature within the appropriate temperature range.As a result, degradation of the catalyst can be suppressed.

(6) As shown in FIG. 2 , engine 13 includes turbocharger 47 which usesenergy of exhaust gas emitted from engine 13 to boost suctioned air tobe fed to engine 13. As shown in FIG. 4 , the boost line L2 determinedon the map is such that turbocharger 47 boosts suctioned air when thetorque generated by engine 13 indicated by an operating point on the mapexceeds the boost line L2. As shown in FIGS. 10 and 11 , when the torquegenerated by engine 13 indicated by the operating point on the map isbelow the boost line L2, HV-ECU 62 shifts the operating point to exceedthe boost line to allow the catalyst to have a temperature within theappropriate temperature range or lower for a longer period of time thanwhen the operating point is not shifted.

Thus the catalyst can have a temperature within the appropriatetemperature range or lower for an increased period of time. As a result,degradation of the catalyst can be suppressed.

Although the embodiments of the present invention have been described,it should be considered that the embodiments disclosed herein areillustrative and non-restrictive in every respect. The scope of thepresent invention is defined by the terms of the claims, and is intendedto include any modifications within the scope and meaning equivalent tothe terms of the claims.

What is claimed is:
 1. A hybrid vehicle comprising: an internalcombustion engine; a rotating electric machine; a planetary gearmechanism to which the internal combustion engine, the rotating electricmachine and an output shaft are connected; a catalyst that purifiesexhaust gas of the internal combustion engine; and a controller thatcontrols the internal combustion engine and the rotating electricmachine, wherein the controller controls the internal combustion engineand the rotating electric machine to perform catalyst temperaturecontrol to shift an operating point on a map representing a relationshipbetween rotation speed of the internal combustion engine and torquegenerated by the internal combustion engine so that the catalyst has atemperature within an appropriate temperature range, wherein thecontroller shifts the operating point on an isopower line.
 2. A hybridvehicle comprising: an internal combustion engine; a rotating electricmachine; a planetary gear mechanism to which the internal combustionengine, the rotating electric machine and an output shaft are connected;a catalyst that purifies exhaust gas of the internal combustion engine;and a controller that controls the internal combustion engine and therotating electric machine, wherein the controller controls the internalcombustion engine and the rotating electric machine to perform catalysttemperature control to shift an operating point on a map representing arelationship between rotation speed of the internal combustion engineand torque generated by the internal combustion engine so that thecatalyst has a temperature within an appropriate temperature range,wherein when the catalyst has a temperature lower than the appropriatetemperature range the catalyst is poisoned by a prescribed substance andthus has its purifying ability impaired, whereas when the catalyst has atemperature within the appropriate temperature range or higher thecatalyst is recovered from poisoning and thus has its purifying abilityrestored, and the controller controls the internal combustion engine andthe rotating electric machine to perform the catalyst temperaturecontrol when a condition for recovering the catalyst from poisoning issatisfied.
 3. The hybrid vehicle according to claim 2, wherein theinternal combustion engine includes a forced induction device that usesenergy of exhaust gas emitted from the internal combustion engine toboost suctioned air to be fed to the internal combustion engine, a boostline is determined on the map, and the forced induction device boostssuctioned air when the torque generated by the internal combustionengine indicated by an operating point on the map exceeds the boostline, and when the torque generated by the internal combustion engineindicated by the operating point on the map exceeds the boost line, thecontroller shifts the operating point below the boost line to allow thecatalyst to have a temperature within the appropriate temperature rangeor higher for a longer period of time than when the operating point isnot shifted.
 4. A hybrid vehicle comprising: an internal combustionengine; a rotating electric machine; a planetary gear mechanism to whichthe internal combustion engine, the rotating electric machine and anoutput shaft are connected; a catalyst that purifies exhaust gas of theinternal combustion engine; and a controller that controls the internalcombustion engine and the rotating electric machine, wherein thecontroller controls the internal combustion engine and the rotatingelectric machine to perform catalyst temperature control to shift anoperating point on a map representing a relationship between rotationspeed of the internal combustion engine and torque generated by theinternal combustion engine so that the catalyst has a temperature withinan appropriate temperature range, wherein the catalyst degrades when ithas a temperature higher than the appropriate temperature range, and thecontroller controls the internal combustion engine and the rotatingelectric machine to perform the catalyst temperature control when thecatalyst has a temperature exceeding the appropriate temperature range.5. The hybrid vehicle according to claim 4, wherein the internalcombustion engine includes a forced induction device that uses energy ofexhaust gas emitted from the internal combustion engine to boostsuctioned air to be fed to the internal combustion engine, a boost lineis determined on the map, and the forced induction device boostssuctioned air when the torque generated by the internal combustionengine indicated by an operating point on the map exceeds the boostline, and when the torque generated by the internal combustion engineindicated by the operating point on the map is below the boost line, thecontroller shifts the operating point to exceed the boost line to allowthe catalyst to have a temperature within the appropriate temperaturerange or lower for a longer period of time than when the operating pointis not shifted.